Green and non-destructive separation of cathode materials from aluminum foil in spent lithium-ion batteries

The environmentally-friendly and efficient separation of cathode materials from aluminum (Al) foil is crucial in the recycling process of spent lithium-ion batteries (LIBs) for production of new ones. Here we report a new strategy for such separation. The strategy is based on the combination of a newly-developed green deep eutectic solvent (DES) assisted with microwave treatment to decompose binders in spent LIBs cathode materials. Using this strategy we have achieved a 100 % peeling-off rate of cathode materials from Al foil. The optimum reaction condition for the peeling-off is found as follows: a temperature of 120 °C, a duration of 8 min, and a molar ratio of choline chloride (ChCl): ethylene glycol (EG) of 1: 2. The DES system can be reused up to 9 times. Both the experimental results and the density functional theory (DFT) calculation indicate that DES effectively reacts with polyvinylidene fluoride (PVDF) polymer chains, thereby facilitating the separation of active materials from Al foil. The separation mechanism is ascribed to the dissolution of PVDF by the DES through two reaction paths: 1) the formation of C = C bonds during degradation; 2) the formation of C = O bonds during further oxidation. The established separation strategy is of great promise for industrial applications owing to its environmental-friendliness and high-efficiency.